ES2950657T3 - Flow measurement - Google Patents

Abstract

An arrangement 5 of acoustic transducers (7a, 7b, 7c, 7d, 9a, 9b, 9c, 9d, 11a, 11b, 11c, 11d, 13a, 13b, 13c, 13d) for a flow meter. The flow meter is used to measure the speed at which the fluid flows. The arrangement includes a respective set of transducers (7, 9, 11, 13) for each edge of a theoretical regular polygon NRP. The transducer assemblies are associated with a tubular cavity to transport the fluid. Each of the transducer arrays respectively includes two acoustic transducers oriented to define an acoustic path that lies in a measurement plane MP7 of the respective array, and two other acoustic transducers oriented to define another acoustic path that lies in the measurement plane of the respective set. The transducer arrays are positioned such that, in the cross section normal to the tubular cavity, the measurement plane of each respective transducer array coincides with a respective edge of the theoretical regular polygon. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Flow measurement

The present application claims priority to Australian provisional patent application 2017900133 filed on January 17, 2017.

FIELD OF THE INVENTION

The invention relates to flow measurement.

The invention will be described in relation to the measurement of the rate at which irrigation water flows, although variants of the invention may be applied in other contexts, for example, applied to the measurement of the rate at which a gas flows.

BACKGROUND OF THE INVENTION

A conventional method for measuring the speed at which water flows through a pipe involves installing a pair of acoustic transducers facing each other to define an acoustic path. The path passes through the tubular interior of the pipe at an angle of 45° with respect to the central axis of the pipe and bisects that axis. Each of the transducers sends signals along and receives signals from the acoustic path. From the output of these transducers, the transit time of these signals in each direction along the acoustic path can be determined. One difference between these transit times is related to the average axial velocity of the fluid within the pipe.

The velocity calculation is based on the assumption that the flow is parallel to the central axis of the pipe and that a laminar flow profile exists. The relevant logic is derived using physical analysis.

In practice, these assumptions are not met. Turbulence results in flow patterns that have velocity components that are not parallel to the central axis and a flow profile that is not completely laminar. As such, turbulence within the pipe reduces measurement accuracy.

To improve accuracy, it is conventional to include a second pair of acoustic transducers arranged to define a second acoustic path that intercepts, at 90°, the first-mentioned acoustic path at the centerline of the pipe. The common plane occupied by the two acoustic paths coincides with the center line of the pipe and is called the measurement plane. Of course, only a practical degree of precision is required, rather than absolute geometric precision, and that is how "measuring plane" and similar terminology is used in this art and in this patent specification. As an example, in the context of a 0500 mm pipe, two acoustic paths that intersect with a difference of one millimeter are within a common plane as used herein.

While the addition of a second acoustic path is an improvement, turbulence remains a source of inaccuracy. Consequently, it remains desirable to minimize turbulence reaching the flow meter. To this end, it is common practice to provide:

• on the upstream side of the flow meter, a straight length of pipe at least ten pipe diameters long; and

• on the downstream side of the flow meter, a straight length of pipe at least four pipe diameters long.

In many applications, installing such a straight length of pipe is a costly inconvenience and/or greater precision is desirable. An example of a state-of-the-art acoustic transducer arrangement is found in the international patent application published as WO 2010/002432 A1.

The initial applicant has previously developed improvements over these conventional approaches, such as improvements disclosed in international patent applications published as WO 2011/020143 A1 and WO 2016/004471A1.

Document WO 2011/020143 A1 discloses an arrangement of acoustic transducers that define separate measurement planes, parallel to each other, in the direction of the current. It also discloses an arrangement of transducers that define a trio of current measurement planes, each of which intersects the centerline of the pipe at a different angle, so that the circular cross section of the pipe is divided into six sectors.

WO 2016/004471 A1 discloses a tubular cavity which is also divided by measurement planes into sectors. A gate valve is located downstream and adjacent to the transducer arrangement. System identification is used to relate flow rate, gate valve position, and transducer outputs.

The term "system identification" refers to the well-known technique of deriving a system model from experimental data. It consists of suggesting an appropriate mathematical representation for the model of the system of interest, followed by a fitting process in which the particular representation is optimized to reproduce as closely as possible the timed experimental observations of the system. The methodology provides a means to compare different models and classify them according to their ability to reproduce system behavior. System identification is a particular subtopic in mathematical systems theory and also in statistics. Despite the initial applicant's prior improvements, the present inventors have recognized that additional improvements are still possible. Preferred forms of the present invention are intended to provide improved precision and/or simpler and more convenient construction.

A reference herein to a patent document or other subject matter given as prior art should not be taken as an admission or suggestion that the document or subject matter was known, or that the information it contains was part of the prior art. common general at that time. the priority date of any of the claims.

SUMMARY OF THE INVENTION

One aspect of the invention provides an arrangement of acoustic transducers for a flow meter according to claim 1. Preferred embodiments are described according to claims 2-19.

A regular polygon is a plane shape consisting of a chain of straight line segments (called "edges" or "sides") that is equiangular (all angles have the same measure) and equilateral (all sides have the same length). . Regular polygons can be convex or star-shaped. Triangles, squares, pentagons and hexagons, etc., are examples of regular convex polygons. Pentagrams and hexagrams are examples of regular star polygons.

Preferably, the acoustic path of each respective array substantially crosses the other acoustic path of the respective array. Most preferably, the acoustic path of each respective array is substantially perpendicular to the other acoustic path of the respective array. The theoretical regular polygon may be substantially concentric to the tubular cavity and is preferably convex. Most preferably, the notional regular polygon is a square.

The measurement planes are preferably substantially parallel to the tubular cavity.

The arrangement may include four further acoustic transducers oriented to define two acoustic paths located in a plane coincident with a center line of the tubular cavity.

Preferably, each upstream acoustic transducer, of the assemblies and of the four additional acoustic transducers, is located in an upstream plane transverse to the tubular cavity; and each downstream acoustic transducer, of the assemblies and of the four additional acoustic transducers, is located in a downstream plane transverse to the tubular cavity.

This aspect of the invention also provides a hardware arrangement that includes the arrangement of acoustic transducers and a sensor for detecting the level of the fluid in the tubular cavity.

This aspect of the invention also provides an assembly for a flow meter including the arrangement; and a body that defines the tubular cavity and that carries the acoustic transducers.

Preferably, the body defines a respective mounting face portion for each of the acoustic transducers of the assemblies; each of the mounting face portions being substantially normal to a respectively corresponding edge portion of the theoretical regular polygon.

This aspect of the invention also provides a flow meter including the arrangement; and a logical arrangement for applying the logic to the outputs of the transducers to produce an indication of the rate at which the fluid is flowing.

Preferably, the logic is determined, at least in part, by the system identification.

Brief description of the drawings

One embodiment of the apparatus will now be described, by way of example only, with reference to the following drawings, in which:

Figure 1 is an axial cross-sectional view of an assembly for a flow meter;

Figure 2 is an end view of the assembly;

Figure 3 is a perspective view of the assembly;

Figure 4 is a sharper perspective view of Figure 3;

Figure 5 is a perspective view of another assembly for a flow meter;

Figure 6 is an axial cross-sectional view of a transducer unit installed for the assembly of Figure 5;

Figure 7 is a perspective view of another assembly for a flow meter;

Figure 8 is an axial cross-sectional view of another assembly for a flow meter;

Figure 9 is an end view of the assembly;

Figure 10 is a perspective view of the assembly of Figure 9;

Figure 11 is a perspective view of the assembly shown in Figure 1 with a folding valve attached thereto;

Figure 12 is a vertical axial cross-sectional view of another assembly for a flow meter;

Figure 13 is a horizontal axial cross-sectional view of the assembly; and

Figure 14 is a perspective view of the assembly shown in Figure 1 with a knife gate valve attached.

DETAILED DESCRIPTION

Figures 1 to 4 illustrate an assembly 1, for a flow meter, incorporating a tubular body 3 and an arrangement 5 of acoustic transducers.

Body 3 defines a tubular cavity through which water flows. In this case, the tubular cavity has a diameter of OD. The body 3 may have mounting features (such as mounting flanges) within a diameter D upstream and downstream of the transducers to allow the assembly to be conveniently installed along a pipeline. Alternatively, the transducers may be mounted in another manner to measure flow through the tubular cavity of the pipeline per se. Variants of the described arrangement may be used in the context of non-circular pipes.

Arrangement 5 includes four sets 7, 9, 11, 13 of acoustic transducers.

The preferred forms of arrangement 5 are useful for measuring flow in any direction, although for present purposes flow in the direction of arrow Q in Figure 1 will be considered.

The assembly 7 includes transducers 7a, 7b, 7c, 7d mounted in the vicinity of the interior of the body 3. An upstream one 7a of these transducers cooperates with a downstream one 7b (Figure 4) to define a diagonal acoustic path through a flat upper chord of the cylindrical cavity of the body 3. The other 7b upstream of those transducers sits symmetrically to the transducer 7a on the other side of the vertical center line CL (as drawn) of the arrangement in the same transverse plane as the transducer 7a and in the same axial plane as transducer 7d. The transducer 7b cooperates with one downstream of the transducers 7c to define another acoustic path. Both acoustic paths defined by array 7 lie on a common measurement plane MP7. The transducers 7a, 7b, 7c, 7d are thus located at the corners of a fictitious square through which the acoustic paths extend diagonally from corner to corner.

Assembly 9 includes acoustic transducers 9a, 9b, 9c, 9d. Transducer 9a sits adjacent to transducer 7a and transducer 9c also sits adjacent to transducer 7c. Transducers 9b, 9d sit vertically below transducers 9a, 9c respectively. The transducer 9a cooperates with the transducer 9d to define an acoustic path ACg,1 that diagonally traverses a vertical chord inside the body 3. The transducers 9b, 9c also cooperate to define a second acoustic path AC92 diagonally through the same chord. These trajectories are preferably mutually perpendicular as suggested in Figure 1.

The trajectories AC9,1, AC92 lie on a common measurement plane MP9. Sets 11 and 13 also define the measurement planes MP11, MP13.

In the cross section inside the body 3 (corresponding to Figure 2), the measurement planes each extend along a respective edge of a theoretical regular polygon NRP in the shape of a square. The vertices of the NRP polygon are defined by the points where two of the measurement planes intersect each other.

The exemplary arrangement 5 further includes a set 15 of acoustic transducers 15a, 15b, 15c, 15d that define a crossed pair of acoustic paths coincident with a central axis CA of the tubular interior of the body 3 to define a central measurement plane MPC. In this example, the central measurement plane MPC is horizontal.

The present inventors have found that the described construction is advantageous from both computational and construction points of view.

The acoustic transducers are configured to produce outputs to which logic can be applied to determine the average axial velocity of the fluid along each of the measurement planes. While the applicable logic may vary from one arrangement to another and depend on the nature of the flowing fluid, the inventors' laboratory experiments have shown that surprisingly accurate flow measurements can be obtained by applying, at the output of the transducers, the logic that has been developed by system identification.

It has been found that the described arrangement of acoustic transducers takes into account spiral flow conditions, known as eddies, better than existing detection arrangements. Swirl is an aspect of turbulence.

Conventional transit time-based flow measurement involves acoustic trajectories that transect the central axis of the pipe and is based on assumptions regarding the flow profile within the pipe. The disclosed preferred arrangement of acoustic transducers includes acoustic paths that do not transect the central axis to provide the data necessary to compensate for swirl.

Preferred forms of the invention are particularly advantageous in the context of circular pipes (i.e. pipes of circular cross section) where swirl is more problematic.

Some constructional advantages arising from this arrangement of transducers are best illustrated with respect to the example arrangement of Figures 5 and 6. For convenience, reference numbers have been transferred for components analogous to those of Figures 1 to 4.

Each adjacent pair of transducers may be mounted within a single transducer unit, for example, one transducer unit 17' may carry the transducers 7c, 9c. As such, eight mutually identical transducer units can be mounted to accommodate the sixteen transducers of sets 7, 9, 11 and 13, for example, unit 17 illustrated is identical to unit 17'.

The transducer unit 17 also includes a mounting arrangement in the form of a mounting plate 19 whereby the unit 17 can be mounted as a unit and in association with the tubular interior of the body 3. The mounting plate 19 is curved to complement the exterior of the body 3 and has an arrangement of through holes 21 through which suitable fasteners can be passed to engage the complementary holes 23 formed in the wall of the body 3, while a transducer carrying portion 25 of the unit protrudes through a complementary opening 27 through the body wall 3. The transducer carrying portion 25 contains a pair of transducers, for example, transducers 7c, 9c directed at the angles required for operation. A gasket 29 surrounds the opening 27 and is compressed to seal against leakage through the opening 27.

With proper adjustments to the mounting arrangement, the same transducer unit 17 can be used on pipes of different diameters.

Figure 7 illustrates another example of assembly 1 in which mutually adjacent acoustic transducers are separated from each other by flow separation fins. In this example, the flow separation fins extend parallel to the tubular interior of the housing 3, for example, fin 30 mutually separates the transducers 7a, 9a while fin 31 mutually separates the transducers 9b, 11b. The fins straighten the flow and limit the effects of eddy and crossflow. Similar fins 30a and 31a are located in front of fins 30 and 31. Fins 30, 31, 30a and 31a may have any suitable shape and typically extend beyond the height of the transducers to better straighten the water flow.

Other forms of flow separator structure are possible. In the example of Figures 8 and 9, the transducers 7a, 9a are separated by a flow separator structure in the form of a longitudinal projection 33 that defines a mounting face 35 substantially perpendicular to the upper edge of the theoretical rectangular polygon NRP and in the that the transducer 7a can be mounted. The projection 33 also defines a mounting face 37 of the transducer 9a and substantially perpendicular to the lateral edge of the NRP polygon. This construction allows a common transducer and transducer mounting arrangement to be used at all sixteen points in the arrays. A similar effect could be achieved if each transducer mounting face had some other common orientation (i.e., non-perpendicular) as shown in Figure 10 relative to the corresponding portion of the theoretical rectangular polygon. In Figure 10, the longitudinal projections 41 have angled mounting faces 43, 45 opposite the perpendicular mounting faces 35, 37 of Figure 9.

In the examples of Figures 1 to 7, each of the acoustic paths spans a respective distance in the direction of the stream and, as such, each pair of acoustic transducers facing each other includes an upstream transducer and a downstream transducer, for example, the pair 9b, 9c includes the upstream transducer 9b of the downstream transducer 9c.

In the examples illustrated so far, the upstream transducers are in a common transverse plane inside the body 3 while the downstream transducers are located in another common transverse plane. This coincidence is not essential. As illustrated in Figures 8 to 9, transducers adjacent to each other, such as transducers 7a, 9a, may be axially offset from each other. Preferably, the acoustic paths intersect at least one common plane transverse to the tubular cavity of the body 3, that is, preferably, the dimension L of Figure 8 is at least zero.

Figures 12 and 13 illustrate an assembly, for a flow meter, similar to the assembly of Figure 1. With respect to the variant of Figure 1, the additional acoustic sensors 15a, 15b, 15c, 15d have been moved axially inwards towards the center of the array so that they lie in the upstream and downstream planes UP, DP in which the acoustic transducers of the array also reside. This movement reduces the overall length of the flow detection arrangement. This movement results in the acoustic paths AC-i5,1, AC-i5,2 crossing at an angle other than the conventionally preferred 90°. However, together with the output of the equipment's acoustic transducers, accurate flow measurements can be obtained.

The arrangement of Figure 12 further includes a water level sensor 39 for detecting the water level WL in the pipe. In this example, sensor 39 is a top-mounted acoustic sensor that sends signals and receives reflected signals from a vertical acoustic path AC39. Other water level sensing arrangements are possible, for example a ground mounted sensor may be provided. The water level may be expressed in terms of height above the bottom of the pipe, or in terms of height below the outside of the pipe, or in other terms.

Preferred forms of flow meter process data from the acoustic transducers and also from the sensor 39 to allow measurement of flow in the pipes when they are full and also when they are only partially full.

The examples shown in Figures 1 to 10 and 12 to 13 relate to the measurement of in-line flow through a body or pipe 3. Embodiments may also include the attachment of a flow control device or gate to allow water to pass through. Such devices can be installed anywhere along the pipe 3, or at the end of it, depending on the requirements. Figures 11 and 14 show the use of typical flow control devices used in the field, but are not limited to such devices as will be understood by those skilled in the art.

Figure 11 has a folding gate 51 fixed to the end of the tube 3. Such a gate is fully described in the embodiments discussed in Australian Patent No. 2012234917. A pair of hinged sealable semicircular plates 53 (only one of which is visible in Figure 11) can be raised and lowered by pivoting struts 55 articulated to a rotating threaded element 57 contained in an activation device 59. A motor 61 will rotate the threaded element 57 under the control of the program. The 61 motor can also be replaced with a crank, if necessary.

Figure 14 has a knife gate valve 63 fixed to the end of the pipe 3. Such a valve is fully described in the embodiments discussed in international patent applications WO 2011/020143 and WO 2016/004471. A door leaf 65 that slides tightly within a frame 67 can be raised and lowered by the lifting mechanism 69 connected to the frame 67. A motor 71 will operate under program control to raise and lower the door leaf 65. The 71 motor can also be replaced with a crank, if necessary.

The skilled person will appreciate that the present teachings can be extended well beyond the examples described. The invention is not limited to the examples described; rather it is defined by the claims. As an example, some variants may dispense with assembly 15, and while in this example the measurement planes of the assemblies are parallel to the interior of the tubular body, in other variants this may not be the case.

In this example, there are ten pairs of acoustic transducers facing each other corresponding to ten acoustic paths. This arrangement has been found to lead to flow measurements less affected by crossflow effects and other aspects of turbulence than other flow measurement arrangements. Of course, the principles disclosed can be extended beyond a theoretical square to other regular polygons, for example to theoretical regular polygons in the form of pentagons or pentagrams, in which case similar computational and construction benefits could be obtained.

Claims (17)

1. An arrangement of acoustic transducers for a flow meter suitable for water irrigation; the flow meter providing measurement of the speed at which water flows; the arrangement including a respective set of transducers (7, 9, 11, 13) for each edge of a fictitious regular polygon; the transducer sets (7, 9, 11 13) being mounted in a tubular cavity (3) to transport the water; including each of the transducer sets (7, 9, 11,.13) respectively two acoustic transducers (7a, 7b) oriented to provide a single acoustic path to each other and located in a measurement plane (MP7) of the respective assembly; and two other acoustic transducers (7c, 7d) oriented to provide another single acoustic path between themselves and located in the measurement plane (MP7) of the respective assembly; and the sets of transducers being positioned so that, in the cross section normal to the tubular cavity, the measurement plane of each respective set of transducers coincides with a respective edge of the theoretical regular polygon; characterized by the arrangement including transducer units (17), each of which carries two of the acoustic transducers (7a, 9a) and includes a mounting arrangement (19) whereby the respective one is mounted as a unit at least partially within the tubular cavity wall (3). 2. The arrangement of claim 1, wherein the acoustic path of each respective assembly substantially crosses the other acoustic path of the respective assembly. 3. The arrangement of claim 1 or 2, wherein the acoustic path of each respective assembly is substantially perpendicular to the other acoustic path of the respective assembly. 4. The arrangement of claim 1, 2 or 3, wherein the theoretical regular polygon is substantially concentric to the tubular cavity (3). 5. The arrangement of any one of claims 1 to 4, wherein the theoretical regular polygon is convex. 6. The arrangement of any one of claims 1 to 4, wherein the regular polygon is a square. 7. The arrangement of any one of claims 1 to 6, wherein the measurement planes are substantially parallel to the tubular cavity (3). 8. The arrangement of any of claims 1 to 7 that includes four other acoustic transducers oriented to define two acoustic paths that lie in a plane coincident with a center line of the tubular cavity. 9. The arrangement of claim 8, wherein each upstream acoustic transducer of the assemblies and the four additional acoustic transducers is located in an upstream plane transverse to the tubular cavity; and each downstream acoustic transducer, of the assemblies and of the other four transducers, is located in a downstream plane transverse to the tubular cavity. 10. A hardware arrangement including the arrangement of any of claims 1 to 9; and a sensor (39) to detect the water level in the tubular cavity (3). 11. An assembly for a flow meter including the arrangement of any of claims 1 to 10; and a body that defines the tubular cavity and that carries the acoustic transducers. 12. The assembly of claim 11, wherein the body defines a respective mounting face portion for each of the acoustic transducers of the assemblies; each of the mounting face portions being substantially normal to a respectively corresponding edge portion of the theoretical regular polygon. 13. A flow meter including the arrangement of any of claims 1 to 10 and a logic arrangement for applying logic to the outputs of the transducers to produce an indication of the rate at which water flows. 14. The flow meter of claim 13, wherein the logic is determined, at least partially, by the system identification. 15. A flow control unit including the flow meter of claim 13; and a flow control barrier to control the movement of water inside. 16. The flow control unit of claim 15, wherein said flow control barrier is a knife gate valve (63). 17. The flow control unit of claim 15, wherein said flow control barrier is a folding gate valve (51).